Method and device for manufacturing glass panes of any desired contour from sheet glass

ABSTRACT

The invention relates to a method for producing glass panes of any desired contour from sheet glass, comprising the following steps: scribing scribe lines into a least one face of the sheet glass along the contour down to a depth T  glass pane?, using a cutting device, and positioning the glass pane on a support. The inventive method is further characterized in that a defined force F is applied to the sheet glass so that it breaks along the scribe lines, said break extending through the entire thickness of the sheet glass.

[0001] The invention relates to a method for manufacturing glass platesof any contour from flat glasses, a separation line being driven, in afirst stage, along a contour up to a predetermined depth in at least oneside of a glass plate by means of a cutting device. Then, the glassplate is positioned and severed from the flat glass along the contour.The method is more specifically intended for manufacture of glasssubstrates for electronic storage media.

[0002] In addition to the method, the invention also provides a devicefor breaking glass plates of any contour out of flat glass. The deviceas well is more specifically directed to be used for manufacturing glasssubstrates for electronic storage media with an outside diameter and aninside diameter from a glass plate, such a device being comprised of abase pad and of a pressing facility.

[0003] Glass substrates for magnetic storage media, more specificallyhard disks, are currently mainly made use of in laptop applications. Theadvantage of glass substrates over the currently widely used aluminiumsubstrates lies in the increased rigidity, hardness, E-module and, as aresult thereof, in the better resistance from impacts and the reducedfluttering.

[0004] Heretobefore, the applicability of glass substrates for magneticstorage media, more specifically hard disks, was made difficult becauseglasses with suited surface properties could only be provided with veryhigh expense of technique.

[0005] This more specifically applies to the manufacturing of glasssubstrates by pressing and floating but also to glass ribbonsmanufactured by way of a drawing method as disclosed for example in U.S.Pat. No. 5,725,625.

[0006] With the drawn glass ribbons according to U.S. Pat. No.5,725,625, the surface of the drawn glass must be subjected to twolapping steps and to two additional polishing steps.

[0007] A novel method as it is explained in the application Ser. No.09/477,712, filed in the U.S. Patent Office on Jan. 5, 2000, thedisclosure of which is fully incorporated herein, permits to achieve adrawn glass substrate that has a flatness ≦25 μm, more specifically ≦10μm, a waviness <100 Å, more specifically <40 Å, a thickness variation of±20 μm, more specifically ±15 μm, and a surface roughness <10 Angström,more specifically <5 Å.

[0008] The surface properties, flatness, waviness and surface roughnessare determined according to the known method like for example standardmeasurement methods for display substrates as described in SEMI D15-1296of SEMI (1996). The term flatness is to be construed as the departurefrom an ideal flat surface measured over the entire surface, the termwaviness as the mean wavelength part of the departure from an idealsurface related to a medium sized reference distance and the termsurface roughness as the departure in the short wavelength range relatedto a short distance of measurement for evaluation. Such good surfacesneed no longer be finished as this is for example the case with thesurfaces according to U.S. Pat. No. 5,725,625. For glass substrates, itis therefore desirable to indicate methods for manufacturing electronicstorage media with which the surface finishing process may be dispensedwith altogether or be considerably reduced.

[0009] Current state of the art methods are not suited for furtherprocessing the drawn or floated glass ribbons with a flatness ≦25 μm, awaviness <100 Å, a thickness variation of ±20 μm, and a surfaceroughness <10 Å that must be cut so as to obtain smooth edges, with anypredetermined contour of the cuts being possible and the surfaces beinglargely prevented from being damaged during processing.

[0010] One approach to avoid both slivers, recesses and microcracks isto separate glass on the basis of thermally generated mechanicalstresses. The beam of a heat source directed onto the glass is therebymoved relative to the glass at a constant speed, a high thermomechanicalstress which causes the glass to crack being generated in the process.This thermomechanical stress is further increased by a cooling spot thatfollows the heat beam. Infrared radiators, special gas burners and morespecifically lasers meet the property requirement placed on the heatsource which consists in being capable of locally positioning thethermal energy, i.e., of positioning it with an accuracy better than onemillimeter, more preferably better than 100 micrometers, whichcorresponds to the typical cutting accuracies. Lasers have provedefficient and have gained acceptance because of their good focusability,the good controllability of performance and the possibility to form thebeam and to thus distribute the intensity on glass. The glass ispre-scribed by the laser beam prior to being mechanically broken. Thismethod is known as the scribe and break process.

[0011] Methods of laser cutting that induce a thermomechanical stressreaching beyond the resistance to breaking of the material by locallyheating it through the focussed laser beam in connection with a coolingstep from the outside have been proposed in EP 0 872 303 A2, DE 693 04194 T2 and DE 43 05 107 C2 as well as in U.S. Pat. No. 5,120,926.

[0012] GB-A-1433563 shows a method in which a separation line is drivenin a glass substrate using a laser, the glass being then broken alongsaid separation line by means of a cutting device which is harder thanglass. Examples of such type cutting devices are diamond or aluminiumcutting devices.

[0013] An alternative scribe and break process is disclosed by U.S. PatNo. 2,372,215. According to this method, a separation line of a depth Tis scribed in a glass surface using a cutting tool, such as a smalldiamond wheel for example, and the glass is then broken by mechanicalaction along said separation line for example.

[0014] In a preferred embodiment, the glass is broken along theseparation line T by introducing on purpose temperature stresses in theglass.

[0015] With the prior art scribe and break techniques, glass substrates,more specifically for electronic storage media, cannot be manufacturedso as to meet the required quality more specifically because of theirthickness.

[0016] It is the object of the invention to indicate a method formanufacturing glass plates of any contour from flat glass, morespecifically glass substrates for storage media, that involves as fewsteps as possible and that enables the manufacturing of individual glasssubstrates for electronic storage media largely without damaging thesurfaces obtained during the glass drawing process. These methods aremore specifically intended not to substantially degrade the surfaceproperties obtained during the glass drawing or floating process whichare: a flatness ≦25 μm, a waviness <100 Å, a thickness variation of ±20μm, and a surface roughness <10 Å.

[0017] In accordance with the invention, the solution to this object isthat, after having positioned the glass plate and using a methodaccording to the preamble of claim 1, a defined force is applied ontothe glass plate using a pressing facility so that the glass plate breaksalong the separation line and said break is driven through the entiresubstrate. In an advantageous embodiment of the invention, there isprovided that the glass plate is turned upside down prior to beingbroken on the base pad so that the side into which the separation orscribe line has been scribed is now lying on the base pad.

[0018] In a first embodiment of the invention, the base pad used has alarge surface with a defined hardness. If the base pad is rotatable, thecenter of the inner or outer circle defined by the for instance annularseparation line may be brought to coincide with the rotation center ofthe base pad or of the work table while the base pad is placed onto theglass plate. A pressure is exerted with a defined force onto the glasssubstrate, using a pressing tool such as a small wheel or a ball. Thethus obtained break is driven completely through the glass plate byrotating the table.

[0019] In an alternative embodiment, the glass is disposed between twoflexible plates. The thus obtained stack is placed onto a ring base forexample, the diameter of which is greater than the diameter defined bythe one contour of the separation line. Then, pressure is exerted fromthe opposite side using a punch, the diameter of the punch being smallerthan that of the aperture. The force exerted by the punch causes theflexible plates and the glass to bend. Tensile stresses develop in thescribed line and the scribed line is driven through the material so thatan external region of a flat glass can be completely severed from aninternal region thereof.

[0020] The advantage of this method more specifically is that theflexible material reliably prevents the border from breaking off undertransverse stresses, thus preventing the surface of the glass substratefrom breaking off and forming recesses.

[0021] In a third method in accordance with the invention, the flatglass out of which the glass plate is to be broken is placed onto aboard provided with a pocket. A vacuum is preferably applied to thepocket so that an annular surface load is created on the plate. Tensilestresses then develop in the scribed line and cause said scribed line tobe driven through the material so that an external region can becompletely severed from an internal region. Due to the for exampleannular shape of the pocket, the tensile stresses are greatest at thescribed line. Instead of applying a vacuum on the underside of theglass, compressed air or fluid pressure may also be utilized on theopposite side.

[0022] All of the methods according to the invention are suited forbreaking or cutting both an internal hole out of the glass plate and thevery glass plate from the flat glass. The terms breaking and cutting areto be construed herein in such a way that the separation line iscompletely driven through the glass substrate without the internalregion and the external region having to be physically separated fromone another.

[0023] In an additional stage of the process, the internal region may beseparated, or the external region isolated, along the separation linesdriven through the flat glass by the step of breaking or cutting. Forthis purpose, temperature differences are built between internal andexternal region and/or between external region and the surrounding flatglass. For this purpose, the internal region may be cooled selectivelywith liquid nitrogen for example. To isolate the external region, thesurrounding flat glass may for example be heated by hot air with atemperature of 200° C.

[0024] The invention will be described in closer detail herein afterwith reference to the drawing in which

[0025]FIG. 1A is a view of a separation line scribed in a flat glasssubstrate using a mechanical cutting device

[0026]FIG. 1B shows how the flat glass is broken along the separationline

[0027]FIGS. 2A and 2B show how a separation line is driven to a depth Tin a flat glass using a laser device

[0028]FIG. 3 shows the breaking of a glass plate on a base pad with apredetermined hardness

[0029]FIG. 4 shows the breaking of a glass plate with a punch incombination with a ring

[0030]FIG. 5 shows the breaking of a glass plate using vacuum.

[0031] In the FIGS. 1A and 1B, a flat glass 1 is severed by scribing andbreaking which is known as the scribe and break process. In a scribe andbreak process, the flat glass 1 is scribed up to a predetermined depthT_(glass substrate) along a separation line 26 using a cutting devicethat is placed onto the surface of the glass 24.

[0032] After the glass is scribed along a separation line using thecutting tool 22, it is broken along the separation line as illustratedin FIG. 2B. The cutting tool 22 may for example be a mechanical cuttingdevice such as a small cutting wheel. It is particularly advantageouswhen the surface 24 of the glass plate is scribed along the separationline using a laser device. A particularly preferred method of lasercutting is described in the FIGS. 2A through 2B.

[0033] When scribing and breaking is performed using a laser cuttingdevice, the surface of the glass is but slightly damaged. Therefore, aprotective coating may be completely dispensed with.

[0034]FIG. 2A shows the fundamental principle of scribing for cutting aring-shaped glass substrate for electronic storage media, in the presentcase a hard disk 100, out of a flat glass 1 by means of a laser beam.The flat glass serving as a starting product typically has a thickness dranging from 0.3 to 5 mm.

[0035] In the example according to FIG. 2A, the laser beam profile isconfigured to form a V-shaped focal spot 102 on the flat glass 1, saidspot being curved according to the circular contour to be severed. It isfollowed by a cooling spot 104 that increases the thermomechanicalstress generated by the laser beam beyond the resistance to breaking ofthe glass. Said cooling spot may for example be realized by blowing acooling gas, preferably cold air or a water-air mixture, thereon. TheV-shaped focal spot may preferably be realized as described in EP 0 873303 A2 for example.

[0036] Other focal spot geometries may be used instead of the V- orU-shaped focal spot 102 illustrated herein.

[0037] The flat glass 1 is severed in two stages.

[0038] In the first stage according to FIG. 2A, the parameters withregard to laser performance, laser beam profile, focus deposition, chartspeed, meaning the speed of the relative motion between focal spot 102,flat glass 1 and cooling 104 are defined in such a manner that athermomechanical stress is built in the glass which scribes said glassto a predetermined depth T. Typically, the depth T of the scribed lineranges from 0.08 to 0.3 mm.

[0039] Both the external contour 106 for the glass substrate and theinternal contour 107 for the inner hole of the glass substrate may bescribed with the thus defined parameters, a mechanically scribed line108 serving in both cases as a prescribed line being formed by means ofthe known methods, a cutting wheel for example. A particular advantageis obtained when the pre-scribed line 108 is continued by a laserscribed line 110 so that it tangentially runs into the circular curve ofthe external and internal contour. This superficial scribing assists inachieving a separation without offset of the closed contours 106 and107.

[0040] According to the invention, the glass is broken along theseparation line as described herein after.

[0041]FIG. 3 shows a first possibility that permits to drive scribedlines formed in the way described herein above by means of a laser forexample and constituting the inside and the outside diameter of a harddisk 100 deep through the thickness thereof. There is provided, inaccordance with the invention, that, after the separation lines for theinside and the outside diameter are laser scribed, the flat glass 1 tobe processed is turned upside down and positioned onto a base pad 200 ofa defined hardness. It is particularly advantageous when the base pad200 is placed on a rotatable work table 202. When using a rotatable worktable, it is advantageous to dispose the glass plate from which thecircular glass substrate, the future hard disk for example, is cut outin such a manner that it enables as exact a superposition of the centerof the hard disk and of the rotation center of the work table 202 aspossible. A pressure is exerted onto the glass substrate 1 by means of apressing facility in the form of a small wheel 204 or of a ball forexample, a defined force F being applied over the separation line forthe outside diameter or over the separation line for the insidediameter. The break line 206 obtained is driven further by rotating thework table 202. The distance from the wheel or the ball may varydepending on the position of the break 206 in the glass substrate. Thisinfluence is compensated for by an adjustable force.

[0042] The hardness of the base pad 200 correlates to the breaking forceto be applied. Generally speaking, the following applies: the lower thehardness of the base pad 200, the lower the breaking force needed. Theprocess is more difficult to control with soft bases, though.

[0043] Furthermore, it has been found out that the positioning accuracyof the wheel 204 on the scribed line 110 influences the angularity ofthe work piece's edge. With wide wheels, the positioning isnon-critical. However, wide wheels are but conditionally usable for thesmall inside diameters on account of the high deflection. For breakingthe inside diameter, the use of a ball is therefore advisable.

[0044]FIG. 4 discloses a method for breaking glass plates out of flatglass 1 that represents an alternative to that illustrated in FIG. 3.The flat glass 1, from which a glass plate of any contour is to besevered, is placed between two flexible plates 300.1 and 300.2 made ofplexiglass. The flat glass 1 is sandwiched between plates 300.1 and300.2 thus forming a kind of stack 302. The stack consisting of the flatglass 1 and the flexible plates 300.1 and 300.2 rests on a base pad 200with an aperture 304. The diameter d_(O) of the aperture is alwaysgreater than the diameter of the separation line d_(KT) which is shapedlike an arc of a circle.

[0045] To cut the glass plate out of the flat glass along the separationline, a pressure is exerted, from the side 304 opposite the aperture,with a force F by means of a punch 306 for example. The punch 306 has adiameter d_(S) that is smaller than the diameter of aperture d_(O). Theforce F causes the flexible plates 300.1 and 300.2 and the flat glass 1to bend. A tensile stress is thus generated in the scribed or separationline 110. The force F drives the scribed line through material 1 so thatthe external region of flat glass 308.1 is completely severed from theinternal region 308.2 which corresponds for example to the contour ofthe glass plate to be cut out and, as a result thereof, to the outsidediameter. With the method according to the second embodiment of theinvention it is particularly advantageous that the flexible material300.1, 300.2 surrounding the flat glass 1 prevents it from breaking offat the border as a result of transverse stresses. Further, the surfaceof the flat glass is protected.

[0046]FIG. 5 shows a third method according to the invention. The flatglass 1 lies on a base pad 200 with an annular pocket 400. The annularpocket has an inside diameter d_(i) that is smaller than the diameterd_(KT) of the circular separation line which corresponds either to theinside or to the outside diameter of the glass plate that is to be cutout of the flat glass. The outside diameter of the pocket d_(A) isgreater than the diameter of the separation line d_(KT) that is shapedlike an arc of a circle. If a vacuum is applied to the pocket viaconnections 402, an annular surface load is exerted on flat glass 1. Theannular surface load creates a tensile stress in the scribed orseparation line 110. As a result thereof, the scribed line is driventhrough the material so that an external region 308.1 is completelyseparated from an internal region 308.2 like in the embodiment accordingto FIG. 4.

[0047] All of the methods described herein above are suited both forcutting or breaking the entire glass plate out of flat glass 1 and forcutting or breaking the internal hole when the glass plate is used toform a hard disk for example. The annular pocket 400 causes the tensilestresses to be greatest at the scribed line. However, the method is alsopossible using a hole-shaped pocket, i.e., a pocket without a centralpart of a diameter D_(i). Then, it must only be ensured that thediameter D_(A) of such a hole-shaped pocket is greater than the diameterof the separation line D_(KT) that is shaped like an arc of a circle.

[0048] In an alternative embodiment, compressed air may be applied onthe side opposite the pocket instead of applying, via a vacuumconnection 402, a vacuum on the underside of flat glass 1.

[0049] A concrete exemplary embodiment of the invention will be givenherein after:

[0050] A hard disk plate with an outside diameter of 65 mm and an insidediameter of 20 mm is cut out of a flat glass plate having thedimensions: 80×80×0.7 mm as follows: at first, the upper side is scribedusing a laser cutting device in the following manner: first, the glassplate is scribed with a diamond that forms a prescribed line on theperiphery of the circle. Then, the plate is heated with a laser expandedto form a V-shaped focal spot and is cooled by a jet of ethanol and air.After the separation lines are formed, the inside diameter and theoutside diameter are broken out according to the punch/ring method untilthe following applies: for the inside diameter Ø d(punch)=20 mm,d(ring)=50 mm, h(plexiglass)=2 mm; for the outside diameter Ød(punch)=65 mm, d(ring)=80 mm, h(plexiglass)=2 mm, the punch beingsupplied through a power-controlled linear axis.

[0051] The isolation or separation of the broken or separated parts isperformed with hot air of approximately 200° C. for the outer part andwith liquid nitrogen for the inner part.

[0052] The present method indicates novel scribe and break techniques bymeans of which glass substrates may be broken out of glass plateswithout damaging the surface thereof.

[0053] List of Identification Numerals

[0054]1 flat glass

[0055]22 cutting tool

[0056]24 glass surface

[0057]26 separation line

[0058]100 hard disk

[0059]102 focal spot of the laser

[0060]104 cooling spot

[0061]106 external contour

[0062]107 internal contour

[0063]108 scribed line

[0064]110 laser scribed line

[0065]200 base pad

[0066]202 rotatable work table

[0067]204 wheel

[0068]208 break

[0069]300.1

[0070]300.2 flexible plates

[0071]302 stack

[0072]304 aperture of the base pad

[0073]306 punch

[0074]308.1 internal region

[0075]308.2 external region

[0076]400 pocket

[0077]402 vacuum connection

1. A method of manufacturing glass plates of any contour from flatglasses involving the following steps: 1.1. scribing separation lines(26, 110, 106, 107) of a depth T_(glass substrate) along the contour inat least one side of the flat glass (1) using a cutting device, 1.2positioning the glass plate (1) on a base pad (200), wherein 1.3 thebase pad has a predetermined hardness, 1.4 a defined force F is appliedto the flat glass (1) by means of a pressing facility so that a scribedline is created along the separation lines (26, 110, 106, 107) and 1.5the hardness of the base pad correlates to the force to be applied, 1.6the application of the defined force 1.7 causing the scribed line to bedriven through the entire thickness of the flat glass (1), 1.8 thedefined force to be applied and the hardness of the base pad beingchosen such that, when the scribed line is driven through the entirethickness of the flat glass (1), the border of the glass plate islargely prevented from breaking off under transverse stresses.
 2. Themethod according to claim 1, wherein the glass plates are isolated afterbreaking.
 3. The method according to one of the claims 1 through 2,wherein the glass plates are glass substrates for storage media andwherein the separation line corresponds to a circular separation linethat is assigned an outside and/or an inside diameter.
 4. The methodaccording to one of the claims 1 through 3, wherein the cutting deviceis a laser cutting device or a mechanical cutting device.
 5. The methodaccording to one of the claims 1 through 4, wherein the base pad (200)extends over the entire surface.
 6. The method according to one of theclaims 1 through 4, wherein the base pad has an aperture.
 7. The methodaccording to claim 6, wherein the aperture has a circular contour. 8.The method according to one of the claims 1 through 7, wherein the flatglass is positioned in such a manner that the separation line isoriented towards the aperture or towards the apertures.
 9. The methodaccording to one of the claims 1 through 8, wherein the glass plate (1)is turned upside down prior to placing it on the base pad (200) so thatthe side of the glass plate (1) in which the scribed lines have beenformed is now lying on the base pad (200).
 10. The method according toone of the claims 3 through 9, wherein the base pad (200) is rotatableand the glass plate (1) is positioned on the base pad (200) in such amanner that the rotation center of the base pad (200) coincides with thecenter of the outside and inside diameters defined by the annular firstand second separation lines (106, 107).
 11. The method according toclaim 10, wherein the scribed line created by the application of force Falong the separation line(s) (26, 101, 106, 107) is driven further byrotating the base pad (200).
 12. The method according to one of theclaims 1 through 11, wherein the glass plate (1) is sandwiched betweentwo flexible plates (300.1, 300.2) prior to being placed onto the basepad (200).
 13. The method according to claim 12, wherein the flexibleplates are comprised of plexiglass.
 14. The method according to one ofthe claims 1 through 13, wherein the facility for applying the force Fhas balls or wheels (204) locally applying a force onto the glass plate.15. The method according to claim 14, wherein the facility for applyingthe force applies a variable force.
 16. The method according to one ofthe claims 1 through 13, wherein the facility for applying the force hasa punch (306) with a punch area.
 17. The method according to claim 16,wherein the shape of the punch area corresponds to the contour of theseparation line.
 18. The method according to claim 16 or 17, wherein thepunch area is circular in shape.
 19. The method according to claim 16 or17, wherein the punch area is annular in shape.
 20. The method accordingto one of the claims 1 through 19, wherein the base pad (200) has apocket (400) or a groove.
 21. The method according to claim 20, whereinthe pocket or groove has a shape that conforms to the contour of theseparation line.
 22. The method according to one of the claims 1-22,wherein the force is applied in the form of a liquid, more specificallyof compressed air and/or of a pressure difference, more specifically ofa vacuum.
 23. A device for breaking glass plates of any contour from aflat glass with 23.1 a base pad (200) wherein 23.2 the device has apositioning device for positioning the flat glass to be broken onto thebase pad (200) and means for applying a predetermined force and 23.3 thehardness of the base pad is correlated to the force to be applied todrive the scribed line through the flat glass plate and the hardness ofthe base pad is selected depending on the predetermined force in such amanner that, when the scribed line is driven through the glass, theborder of the glass plate is largely prevented from breaking off undertransverse stresses..
 24. The device according to claim 24, wherein themeans for applying the force F are wheels (204) or balls.
 25. The deviceaccording to claim 25, wherein the means for applying the force F are apunch (306).
 26. The device according to one of the claims 23 through25, wherein the base pad has an aperture the shape of whichsubstantially conforms to the shape of the separation line's contour.27. The device according to one of the claims 23 through 25, wherein thebase pad has a pocket (400).
 28. The device according to claim 27,wherein the pocket has a vacuum connection (402).